This application relates to methods for treating contact lenses and particularly relates to methods for disinfecting lenses with oxidative disinfectants.
Through ordinary use, contact lenses accumulate dirt, proteinaceous matter, microorganisms and the like, all of which can adversely affect both the usefulness of the lens and the health of the eye. Therefore, contact lenses must be cleaned and disinfected regularly.
It is known that certain compounds will readily clean and/or disinfect contact lenses. For example, solutions of peroxides, hypochlorites, persulfates and other oxidative solutions are known to clean and disinfect contact lenses. However, disinfecting soft contact lenses, especially hydrogel lenses, using such oxidative chemical agents presents a particular problem in that the lenses can absorb, into the polymeric matrix, the agents from the disinfecting solutions in which they soak. Such oxidative agents, if left in the lens, will irritate the eye of the wearer if even a small amount of the agent remains on the lens when it is inserted in the eye.
Disinfecting systems are known where a neutralizing agent acts on the oxidative agents in the contact lens solution so that, after the lens has been disinfected, the active agents are neutralized. See U.S. Pat. Nos. 3,911,107 and 4,031,109. After such neutralization, the lens, usually after rinsing, can be worn without danger of irritation. Many of these systems are slow, designed to take many hours, or be an "overnight" regimen.
It is difficult to be certain when the oxidative reagent has been effectively neutralized and the lens is safe to wear. Time-oriented regimens, whereby the neutralization takes a fixed amount of time before the lenses may be safely inserted in the eye, rely on strict compliance with the regimen by the lens wearer. Consumers more easily comply with a lens care format if it is rapid and easy to administer.
Various indicator systems have been incorporated into contact lens disinfection regimens. PCT Application No. PCT/US91/06526 discloses the use of complex redox polymers having repeating bypyridinium units as indicators for determining the presence of an oxidative disinfectant in a contact lens solution. U.S. Pat. No. 4,863,627 discloses the use of known redox indicators such as methylene blue, and triphenylmethane dyes in a contact lens solution regimen. However, most known redox indicators do not produce a rapid color change (i.e. within 5 minutes) at neutral pH when the solution is cold or at room temperature.